Switched aperture surface current measurements

Gibbons, Brian B.

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https://hdl.handle.net/2142/101641 Copy

Description

Title

Switched aperture surface current measurements

Author(s)

Gibbons, Brian B.

Issue Date

2018-05-17

Director of Research (if dissertation) or Advisor (if thesis)

Bernhard, Jennifer

Doctoral Committee Chair(s)

Bernhard, Jennifer

Committee Member(s)

• Franke, Steven
• Schutt-Ainé, José
• Bahl, Gaurav

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• surface current measurement
• surface current probe
• magnetic field probe
• switched aperture measurement
• aperture coupling
• slot coupling
• metrology
• surface currents
• RF currents
• microwave currents
• antenna currents

Abstract

The measurement of induced surface currents on antennas, scatterers, and other structures is important for a variety of reasons, including in-situ measurements and validation of simulated results. Techniques for measuring the complete vector nature of surface currents (magnitude, direction, and phase) have relied on probes that perturb the spatial structure of the field. Provided this perturbation is sufficiently small and/or well-characterized, reasonably accurate results may be obtained. In other words, these methods assume that the perturbed fields are sufficiently similar to the unperturbed fields that measurements of the former may be substituted for values of the latter. In this work, a general theory referred to as a switched aperture surface current measurement is developed that directly obtains unperturbed electric surface current measurements, provided certain conditions on the measurement apparatus are met. The most stringent of these are the requirement for a backplane region, fully isolated from the measurement environment, and the requirement that the environment and sources generating the currents do not change significantly when a measurement aperture is switched between open and shorted states. Provided these conditions are met, the theory removes the conventional measurement probe trade-off between measurement accuracy and probe size, since probe size is conventionally proportional to signal-to-noise ratio and inversely proportional to field disturbance and hence accuracy. This theory should thus allow for the creation of highly accurate surface current measurement apparatuses in special cases. The relevant background and supporting theory are developed here for the switched aperture measurement technique, followed by the development and analysis of two calibration theories necessary to utilize the technique in practice. An in-depth study of a simulated, example measurement apparatus is conducted, which is used to draw a number of conclusions and to propose future work.

Graduation Semester

2018-08

Type of Resource

text

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http://hdl.handle.net/2142/101641

Copyright and License Information

Copyright 2018 Brian B. Gibbons

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